Highly Organized Smectic-like Packing in Vapor-Deposited Glasses of a Liquid Crystal

Glasses of a model smectic liquid crystal-forming molecule, itraconazole, were prepared by vapor deposition onto substrates with temperatures ranging from T substrate = 0.78 T g to 1.02 T g, where T g (=330 K) is the glass transition temperature. The films were characterized using X-ray scattering techniques. For T substrate near and below T g, glasses with layered smectic-like structures can be prepared and the layer spacing can be tuned by 16% through the choice of T substrate . Remarkably, glasses prepared with T substrate values above T g exhibit levels of structural organization much higher than that of a thermally annealed film. These results are explained by a mechanism based upon a preferred molecular orientation and enhanced molecular motion at the free surface, indicating that molecular organization in the glass is independent of the anchoring preferred at the substrate. These results suggest new strategies for optimizing molecular packing within active layers of organic electronic and optoelectronic devices.